. Journal of applied microscopy and laboratory methods. -wise the potassium perchlorate is precipitated atonce. If the solution is too dilute, crystals may notaopear for a considerable period. The addition of alcohol will, in such cases,greatly hasten matters. Rubidium and cesium give a like reaction ; their perchlorates are more insol-uble than that of potassium. Thallium forms a still more insoluble perchlorate. The perchlorates of the elements of the other groups which are generally metwith in ordinary work, are sufficiently soluble not to interfere. Behrens* has recently shown that in the
. Journal of applied microscopy and laboratory methods. -wise the potassium perchlorate is precipitated atonce. If the solution is too dilute, crystals may notaopear for a considerable period. The addition of alcohol will, in such cases,greatly hasten matters. Rubidium and cesium give a like reaction ; their perchlorates are more insol-uble than that of potassium. Thallium forms a still more insoluble perchlorate. The perchlorates of the elements of the other groups which are generally metwith in ordinary work, are sufficiently soluble not to interfere. Behrens* has recently shown that in the presence of potassium permanganate,the perchlorate of rubidium is colored pink. Advantage can be taken of a similar property of the potassium salt to obtainan exceedingly beautiful test, for if the test drop contains sodium permanganate,the potassium perchlorate separating therefrom will be colored. To obtain thisreaction, add to the test drop a little sodium manganate, so as to impart a dis- * van Breukeleveen, Rec. trav. chim. Pays-Bas. XVII, i, Fig. 3fci. and Laboratory Methods. 1125 tinct green, then add a tiny drop of hydrochloric acid, thus converting themanganate into permanganate. The reagent is then allowed to flow in. Thecrystals of potassium perchlorate which separate have the same form as before,but are a beautiful deep rose color, the intensity varying with the amount of per-manganate present. In a few moments the liquid is completely decolorized, andthe precipitated crystals deeply colored. Performed in this way the test is anelegant and very striking one. Exercises for Practice. Try reaction with different salts of potassium. Introduce sodium permanganate into the test drop, and test as above. Try the reaction on the other members of Group I, Make a mixture of K and Na salts. Treat a drop of a solution of thismaterial with perchloric acid, evaporate, treat with the reagent again, and againevaporate, extract the dry residue with alcohol, and test the alcoholi
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